Science-based strategies for quantifying and mitigating the impact of anthropogenic emissions on public health are essential for the sustainability of cities. Similar strategies can also be used to develop and assess the effectiveness of a national defense system against terrorist attacks with airborne biological agents and protect against the spread of airborne diseases and other pathogens. Critical prerequisite for developing such strategies is being able to predict how particulates are transported in real-life urban indoor and outdoor environments. Computational fluid dynamics (CFD) models that can simulate turbulent flow and transport phenomena in urban environments can be used to develop such predictive understanding. However, for CFD models to play a role in predicting the fate and transport of contaminants and pathogens in urban environments it is important to demonstrate their predictive ability through systematic validation studies. Such studies require collecting high-resolution experimental data, both in laboratory settings and the field, which can then be used to ground truth the CFD predictions. Validating the ability of CFD models to predict transport of scalars in complex turbulent flows at field scale is a very challenging undertaking. This is because particulate transport is an inherently lagrangian process, which requires knowledge of fluid trajectories or particle paths rather than measurements of velocity at set points in the flow. Moreover, in turbulent flows the fate of a transported scalar depends sensitively on its initial release location. The purpose of the proposed research is the development of a modeling product capable of: predicting fate and transport of contaminants, identifying contamination sources, and determining rates of remediation. The accuracy and efficiency of this product will stem from the combination of advanced CFD methods and a breakthrough validation process. We propose to employ DNATrax, a revolutionary new technology that is able to produce essentially an infinite number of genetically distinct and environmentally safe micro-particles that can be used as particulate simulants to collect transport data in both indoor and outdoor urban environments. Therefore, the research proposed herein is significant because Integrating DNATrax with advanced, high-fidelity computational models will enable this technology to impact a broad range of problems of major societal significance. Examples of commercial uses for DNATrax include, among others: (1) Part of a comprehensive commercial modeling product to calculate the contribution of each of multiple sources to ambient particulate pollution and enable the implementation of targeted corrective measures; and to predict the fate and transport of particulates in urban environment. (2) In healthcare environments as an air quality monitoring system to prevent dispersion of biological contaminants and reduce airbone related healthcare acquired infections; (3) Military installations and vessels as a challenge agent for biodefense networks; and (4) other hazardous work environments as a quantitative fit test for respirators and integration and interoperability o Personal Protection Equipment.